Transformer.



W. M. AUSTIN. TRANSFORMER.

APPLICATION FILED 313.23, 1911.

- Patented July 28, 191%.

Illllllll gw-q-Nrggggs 'IINVENTOFZ same to be "UNITED STATES PATENT OFFICE.

WALTER M. AUSTIN, OF ZELIENOPLE, PENNSYLVANIA.

TRANSFORMER.

To all whom it may concern:

. Be it known that I, WALTER M. AUSTIN, a citizen of the United States, residing at Zelienople, in the county of Butler and State of Pennsylvania, have .invented new and useful Improvements in Transformers, of which the following is a specification.

This invention relates to alternating current transformers, otherwise known as static transformers and has for meet its objects to reduce the weight and the cost of construction.

Another object is to provide an improved construction of the above character having increased efiiciency and durability.

As is well known, the principal parts of a transformer are the core and the coil or coils surrounding thecore, the core being usually built up out of sheet iron laminae approximately rectangular in shape.

In alternating current transformers, the core losses are proportional to the length of the mean magnetic circuit where the sectional area: of the core and its maximum density of magnetization are constant and the coil losses are proportional to the mean length of the coil turns where the sectional area of the coils and the current density are constant, so that the efficiency of the transformer may be increased by shortening the magnetic circuit or by shortening the mean length of turns in the coils, it being understood that the coil turns must be long enough to surround the core and that tie core must be long enough to envelop the coils.

in designing a transformer, due regard must also be had to practical and economi cal methods of manufacture and to the provision of effective ventilation. Laminae having a circular shape would provide the shortest magnetic circuit for a given area but this shape is undesirable for various reasons, such as the waste of material in punching and the difiiculty in assembling the core on the coils. According to. my in vention, I propose to employ the laminae of hexagonal configuration, which have almost as short a magnetic circuit as a circular area, while permitting the punched out of .a sheet with little or. no waste of material. The hexagonal shape of the lamina thus provides for constructing a core having Specification of Letters Patent. Patented J uly 28, 1914. Application filed February 23, 1911. Serial No. 610,400.

siderably less than that of coils of other.

shapes, for a given'cross sectional area of core. Another advantage of-a circular coil is the lower cost of winding and furthermore, a circular coil is more durable than one with angular turns because the latter tends to bind very tightly on the corners of the core, thus endangering the coil insulation, while lying loosely on the flat sides of the core, which latter naturally increases the sectional area of the coils.

In the accompanying drawing; Figure 1 is a transverse SectionalvieW of a transformer embodying one form of my invention; Fig. 2 an elevational View thereof; Fig. 3 a transverse sectional view of atransformer embodying a slightly modified form of my invention; Fig. 4 an elevational view thereof; Fig. 5 a plan View of a transformer .core, showing one method of building up the core; Figs. 6 and 7 similar views, showing different methods of building up cores for three phase transformers; Figs. 8, 9, and 10, views of sheet metal blanks, showing methods of punching the core lamina to avoid waste of material; Fig. 11 an elevational view of a transformer embodying my invention in which circular coils are employed; Fig. 12a plan view of one of Figs. 1 and 2, the transformer core is built up of laminzc each comprising a punching l and two punchmgs 2, the punchings be ng alternated in the successive layers so as to break joints. The core is built around the 0011 in the usual manner.

In Fig. 9 is shown a sheet metal blank with the punchings l and 2 marked outthereon, to

indicate how the sheet is punched to provide the punchings without waste of material, or punching 2 may be blanked as shown in Fig. 10.

in 3 and t, the legs of the core are not joined together, as shown in Fig. 1 but are separate and each leg is built of lamime, each lamina comprising a punching or element 2 and a punching or element 3, the manner of punching these sections without waste being shown in Fig. 9, or a punching 1 may be cut so as to make two punchings The first lamina is formed of an element :2 and an element 3 having their ends abutting to form a hexagon, and the next lamina is applied with an element 3 superimposed on element 2 of .the first lamina, so as to break joints.

In Fig. 5 is shown one leg of a transformer core built up entirely of punchiugs 3 to form a pieced together helix in the following manner: A punching 3 is first placed in position and then a second punching 3 is applied with. one end thereof abutting one end of the first punching so that, as each punching 3 extends more than halfway around, the opposite end of the sec id punching will be displaced by and overlap the adjacent end of the first punching. A third prmchiug is then applie" with one end abutting the orerlapping end of the second. punching, and so on, thus forming a pieced together helix. It wih be noted that'by this method of construction the number of joints for a giren length of core is reduced as compared with the constructions shown in Figs. 1 and 'Fig. (3 illustrates a transformer cm1struc tion for a three phase transformer in which each lamina is composed of one punching 1, one punching i3, and three piuichings 2, thc three coils e u, 5-7), and c of the different phases being situated as shown.

In 7 is shown another arrangement of laminzc for three phase transformer in which each lamina composed of three punchings -t and six punchings 5, the punclr ing 2' being the same as the punching 3 except that it has one corner clipped oil as shown at 20 in Fig. 9. The method of punching the sections -lis shown in Flf. S.

In order to employ circular coils the transformer may be constructed as shown in Fig. 11. According to this construction, each lamina is made as shown in Figs. 12 and 13, one punching 8 being similar to punching butharing one side bent in the form of curve, as shown we 11 inroh acteristic of the inrolute curve. A circular hole is left in the center when the lamime are titted together and the curve of the bent ends is the iurolute, preferably of said circular hole, although if desired the hole through the core may be larger than the circle of the inrolute.

Each lamina is completed by a punching 2 and a number of such lamina are built up to form each leg of the core. The desired number of legs are arranged in radial. position. surroiuuling the coil, as shown in Fig. ii, the, curre of the outer lamina of one leg closely lining the curve of the outer lamina ot the adjacent leg by reason of the iuvolute shape.

The (:(nistruction shown in Fig. 11 is particularly adapted for large transformers by reason of the large radiating surface provided and the economy of material employed, and as before stated, the circular coil has certain advantages over the rectangular coil. if desired, two sides of a hexagonal core punching may be made longer, so as to (.(llhtl'llCll the core as shown in Fig. 1 1-. and the rmnchings may also be blanked without waste of material, as will be crident from Fig. 13.

in designing the transformer core, the length of the sides of the hexagonal contour are preferably made twice the length of the sides of the hexagonal opening through the lamina, so that in punching from the sheet. there will be no waste of material. (then the hexagon is not regular, as shown in ti and 1:; the width of the openings are made equal to one half the outside width. but the openings mayb' inade as long as desired and still pernri flthc puuchings; to be cut out without waste of material.

it is understood that i do not confine myself to the use of lamina: that can be punched entirely without waste, as there may be times when it will be of advantage to use punchings of hexagonal shape. but of di'llerei'it proportions, such that there might be some waste of material.

Haring now described my inventioii, what I claim, as new and desire to secure by Letters Patent, is:

l. A lamina for a, transformer core having a hexagonal contour and a hexagonal aperture the short diameter of which is equal to one half of the short diameter of the lamina. said lamina being formed of two elements, one having ""0 sides and the other four sides of the hexagonal contour.

fr lamina for a transformer core harmetry of the lamina, said lamina being formed of two blanks, one constituting two and the other four sides of therlaniina.

jacent lemma.

4- A transformer core having radial legs composed of laminae, each lamina having one end bent to an involute curve to permit the bent ends of the laminae to fit snugly together' and form a hollow cylinder.

A transformer core composed of radial legs formed of laminae each having one end bent to the form of an involute curve said bent ends bemg adapted when the core is built up to form a hollow Cylindrical core.

6. A transformer core composed of radial legs formed of laminae each having one end bent, the bent ends of the laminw being fitted together to leave a central circular hole and the ends of the laminae being loent to. the involute of said circular hole.

In testimony whereof I have hereunto set 25 my hand.

WALTER M. AUSTIN.

Witnesses; 4

- A M. CLEMENTB, W; W. MARTIN. 

